Desalination systems are one example of distillation systems in which freshwater is separated from salt water as a distillate. Due to receding freshwater resources, the development of desalination systems are important for the production of usable water from saltwater for consumption and agriculture for example. Examples of desalination systems are found in the following U.S. Pat. No. 5,932,074 to Hoiss; U.S. Pat. No. 4,770,748 to Cellini et al; U.S. Pat. No. 4,302,297 to Humiston; U.S. Pat. No. 4,110,174 to Carson and U.S. Pat. No. 4,078,976 to Spears.
One particular desalination system, described in U.S. Pat. No. 4,536,257 provides an evaporation chamber and a condensing chamber which are connected by a transfer pump for pumping water vapour from the evaporation chamber to the condensing chamber. Evaporation and condensation occur by maintaining pressure in the chambers substantially at the vapour pressure of water at ambient temperatures. A float valve controls release of concentrated salt water from the evaporation chamber. In this arrangement, scale is know to form on the float valve and corresponding valve seat which may affect operation of the system. Furthermore, entrained air in the saltwater coming into the evaporation chamber can reduce the effectiveness of the system, forcing the vacuum pump to do extra work to remove the air which is released in the evaporation chamber. Operation of the vacuum pump consumes considerable power for continued operation.